I've never heard the old non VC being sharper, not that you're wrong, I've just never heard it.

I'm currently using the VC version and I'm fairly happy with it. There's lots of pros (nice wide aperture for the price). The autofocus is fast, but noisy - I can't speak for if this was the case with the non VC version. I do get lens flare in tough conditions.

Regarding the sharpness, Typically I would stop the lens down to f/4 and stay there unless I needed to go to f/2.8. I'm really happy with the performance at f/4 and consider it very sharp. Once I go to f/2.8 I might notice the photo not being so sharp in about 1 in every 20 shots. Depends on the subject of course, sometimes you just won't notice it.

I find the VC nice and I can get shots at 1/10 when I'm holding the camera moderately tight.

The lens is not internal focus, so the lens does extend when you zoom - but the lens does not zoom or rotate when you focus, so polarizers are easy to use with it.

hmm... let's see, what else. I'll just give some shots that I've taken with it.

Buying a F/2.8 & not using it at F/2.8 sounds really...I'll just say not practical.
Get the Tamron 17-50mm without stabilisation. The optical formula in the new one is pretty bad. As for the old one,the F/2.8 is very crisp,sharper even than certain budget zoom lenses at F/5.6.

Well, bought the non vc and really pleased with the optics on the lens..........apart from the small white hair and white specs of dust on the rear of the lens, trapped between the glass.

Shop I bought it from was over the web and they are sending out a replacement straight away.

Its a nice weight and size for the D90, I tried the sigma 24-70 hsm f2.8 and that in my opinion was far too heavy and bulky for the body (also had focusing issues at F2.8 ). I can't fault the build on it, feels solid enough, only time will tell if it lasts long enough.